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SX20AC/SX28AC
8.0 INTERRUPT SUPPORT
The device supports both internal and external maskable
interrupts. The internal interrupt is generated as a result
of the RTCC rolling over from 0FFh to 00h. This interrupt
source has an associated enable bit located in the
OPTION register. There is no pending bit associated with
this interrupt.
Port B provides the source for eight external software
selectable, edge sensitive interrupts. These interrupt
sources share logic with the Multi-Input Wakeup circuitry.
The WKEN_B register allows interrupt from Port B to be
individually enabled or disabled. Clearing a bit in the
WKEN_B register enables the interrupt on the corre-
sponding Port B pin. The WKED_B selects the transition
edge to be either positive or negative. The WKEN_B and
WKED_B registers are set to FFh upon reset. Setting a
bit in the WKED_B register selects the falling edge while
clearing the bit selects the rising edge on the correspond-
ing Port B pin.
The WKPND_B register serves as the external interrupt
pending register.
The WKPND_B register comes up a with random value
upon reset. The user program must clear the WKPND_B
register prior to enabling the interrupt. The proper
Figure 8-1. Interrupt Structure
RTCC
WKED_B
Inte
rnal Da
t
a
Bus
WKED_B
WKPND_B
WKPND_B
From MODE
(MODE = 09)
OPTION
RTE_IE
WKEN_B
1 = Ext. Interrupt through Port B
0 = Power Down Mode, no Ext. Interrupt
STATUS
Port B PIN
Interrupt
PC
Interrupt Stack
PC
000
Overflow
Register
PD bit
From MODE
(MODE = 0A)